1. Field of the Invention
The present invention relates to an image heating apparatus for heating a toner image on a sheet. The image heating apparatus can be used in, for example, an image forming apparatus of the electrophotographic type or electrostatic recording type, such as a printer, a copier, a facsimile machine, and a multifunction machine having a plurality of functions of them.
2. Description of the Related Art
Nowadays, image forming apparatuses need quick response (time from transmission of a print instruction to outputting of an image; hereinafter referred to as wait time). A reduction in the wait time is greatly affected by the warm-up time of a fixing apparatus (image heating apparatus).
A fixing apparatus that uses a thin endless belt having a low heat capacity (hereinafter referred to as belt) is described in Japanese Patent Laid-Open No. 8-305187. Specifically, the fixing apparatus employs the technique of pressing the belt using a ceramic heater from its inside toward a pressure roller and driving and rotating the belt using the pressure roller. The use of that technique aims to reduce the wait time.
In the fixing apparatus employing that technique, because the belt slides on the ceramic heater, a heat-resistant lubricant, such as grease or oil, is applied on the inner surface of the belt. The heat-resistant lubricant reduces the frictional resistance between the inner surface of the belt and the ceramic heater, thus facilitating the rotation of the belt driven by the pressure roller.
The fixing apparatus described in Japanese Patent Laid-Open No. 8-305187 includes blades for removing the lubricant. The blades are disposed on the outer surface of the belt on both ends in the width direction. The blades are included to prevent the lubricant leaking out from the ends of the belt with prolonged use of the fixing apparatus from moving to the outer surface of the belt and adhering to a sheet.
However, because the blades for removing the lubricant in the fixing apparatus described in Japanese Patent Laid-Open No. 8-305187 are in contact with the belt, stability of rotation of the belt may be degraded. The conceivable reason for this is that friction caused by the state where the blades are in contact with the belt acts as a force inhibiting the driven rotation of the belt. If the stability of rotation (running) of the belt is inhibited, supplying heat to a sheet becomes instable, and this may lead to an image defect, such as a fixing failure or gloss unevenness.